There are numerous types of vehicle brake systems, including those that include hydraulically actuated disk brakes. In such a system, engagement of a brake pedal by a driver causes a hydraulic piston and caliper out at the wheel to pinch a rotor therebetween. The hydraulic piston and caliper each carry a brake pad which frictionally interacts with the rotor and can slow it down according to a number of factors, including the coefficient of friction (μ) of the materials.
The coefficient of friction of a brake pad and rotor can be affected by the temperature of the system. For example, if the brake pad is cold, the coefficient of friction can be quite high such that the brake pad grabs the rotor in an aggressive way; this condition is sometimes referred to as ‘grabbing’. If the brake pad is hot, the coefficient of friction can decrease and the brakes can react in a less aggressive fashion. In some instances, the decreased coefficient of friction is significant enough that is noticed by the driver; this condition is sometimes referred to as ‘sail on’.